The present invention relates to food product processing, such as the milling of oats to provide milled oat products such as oat bran and oat flour. More particularly, the present invention is directed towards an improved process for milling oats to provide for oat bran high in β-glucan and to β-glucan enriched whole grain oat flour comprising the enriched oat bran and to low fiber oat flour.
The present invention provides improvements upon the dry milling processing methods for oat groats disclosed in US 2005/0153044 “Methods for preparing Oat Bran Enriched In Beta Glucan and Oat Products Prepared Therefrom (published Jul. 14, 2005 by Hellweg et al.). The present methods differ first in the selection of the high flavor oat groats as the starting material. Second, the methods disclosed have been improved also in that the first bolting oat bran of the '044 application in the present methods is fractionated into a coarse and fine fractions; separately milled in different roll stands and then recombined before further processing as generally described in the '044 application. As a result of these changes, higher throughput rates are obtained. Also, a higher percentage of the valuable oat bran fraction is recovered in the high beta glucan oat flour fraction compared to that achievable in the '044 method.
Cereal grain seeds generally contain a small amount of beta-glucan, with oats and barley being recognized as the richest sources of this material. The naked oat seed, known in the art as a “groat”, typically contains 2-4% by weight β-glucan, depending upon oat variety and other factors such as growing conditions. Barley seeds can typically contain twice as much beta-glucan as groats. Beta-glucan is generally found in higher concentrations in the outermost layers of the seed (i.e., the “bran”). Thus, oat bran contains generally a minimum of 5.5% by weight beta-glucan, and typically contains up to 6% up to less than 7% by weight beta-glucan.
The present invention resides in methods for preparing an oat bran having higher levels of β-glucan content, i.e., higher than about 7%.
Oatmeal and oat bran are popular hot cereal consumer products. Oat based Ready-To-Eat (“RTE”) cereal or breakfast cereals are also popular consumer foods packaged food products. One popular line of oat based RTE cereal products is available in puffed “O” shaped pieces fabricated from a cooked cereal dough comprising whole grain oat flour. Other RTE oat-based products are available in the forms of flakes as well as in the form of biscuits or even other puffed shapes (e.g., numbers or letters).
Improvements in oat processing are known to provide oat flours of improved flavor and stability (see, for example, U.S. Pat. No. 5,523,109 “Oat Flour And Method Of Preparation” issued Jun. 4, 1996 to Hellweg, et al.). In the methods of '109 patent, whole oat groats are steamed for greater times than was then conventional, dry toasted for extended times and milled to provide the improved flavor conditioned oat flour. The improved oat flour can then be used to prepare puffed oat based RTE cereal products especially puffed “O” shaped products. However, the '109 patent does not teach or suggest fractionation of the oat flour so produced or that any benefit would be derived there from.
Such oat based products are popular not only for their taste and texture eating qualities but also because of the nutritional properties of the oats from which these products are prepared. In addition to high levels of protein provided by oats, are known as a good source of soluble fiber. A good description of the literature pertaining to the health discussion on the role of fiber is found in U.S. Pat. No. 4,777,045 (issued Oct. 11, 1988 to Vanderveer et al. and is entitled High Bran Snack) which is incorporated herein by reference.
There is a growing awareness of the health benefits to people associated with soluble fiber consumption, especially reductions in blood serum cholesterol, i.e., antillypercholesterolemic benefits. Total dietary fiber (“TDF”) comprises both soluble dietary fiber (“SDF”) and insoluble dietary fiber (“IDF”). In addition to insoluble fiber, oat and barley whole grain cereal flours contain soluble fiber that predominantly comprise β-glucans.
Thus, whole grain oat flour based RTE cereals are naturally and beneficially high in β-glucan fiber levels due to native 2-4% levels of β-glucan in whole grain oat flour. However, in certain crop years due to vagaries of growing conditions, the native levels of oat bran in whole grain oat flow can be too low to provide the requisite levels of soluble fiber to provide sufficient amounts of soluble fiber per serving of finished RTE cereal such as to characterize the RTE cereal as “heart-healthy”. Also, for even better fiber nutrition, it would be desirable to fortify oat based RTE cereals with β-glucan.
One technique for increasing the soluble fiber content of whole grain oat flour and RTE products prepared therefrom is to fortify the whole grain oat flour with oat bran. Since β-glucan is higher in concentration in oat bran (5.5% to under 7%), the cereal products can be formulated with added levels of oat bran. However, as the concentration of oat bran increases in such products (beneficially increasing the β-glucan content) other properties such as cost increases and puffability correspondingly decrease. Also, while such products are known and are commercially available (such as from Can-Oat Milling, a wholly owned subsidiary of Saskatchewan Wheat Pool, Portage La Prairie, Manitoba, Canada R1N 3W1), such high β-glucan oat bran products are high in price and are produced by methods that are proprietary. Moreover, while such products are higher in β-glucan content, such products do not have the improved flavor profile of the oat flour products prepared by the methods of the Hellweg '109 patent. More recently, methods for producing oat products high in β-glucan have been described in published US patent application US 2003/0087019 A1 published May 8, 2003.
Barley also contains beta glucan. While most barley varieties are bred for low β-glucan content (since β-glucan is inimical to brewing clear beer), some barley varieties are high in β-glucan content. Dry milling methods for preparing a β-glucan rich material from barley are also known and for the provision of RTE cereals prepared there from (see for example, U.S. Pat. No. 5,151,283) “High Soluble Fiber Barley Expanded Cereal and method of Preparation” (issued Sep. 29, 1992 to Foehse et al.). However, the '283 patent teaches that due to the differences between barley and oats, teachings regarding processing of one grain are not transferable between oats and barley. Indeed, commercial milling operations are typically designed and operated to process single grain types. Also, when providing whole grain oat products especially popular puffed RTE products, addition of barley based ingredients can be seen undesirably diluting the oat identity of such products.
Wet extraction methods for preparing β-glucan from oat flours are known (see for example U.S. Pat. No. 6,323,338 “Method for concentrating B-glucan” issued Nov. 27, 2001 to Potter, et al.). The '338 patent teaches that “Previous processes for concentrating beta-glucan from cereals such as oats or barley have proven impractical for commercial manufacturing processes because of high cost and/or low yields.” Notwithstanding described improvements, commercial wet extraction β-glucan methods remain uneconomical for mass produced consumer food products.
Thus, in view of the present state of the art, there is a continuing need for methods for preparing a high β-glucan content oat bran ingredient. There is also a continuing need for less expensive β-glucan extraction techniques compared to known wet extraction methods.
There is also a need for whole grain oat flours enriched with high levels of β-glucan that provide the taste and cook properties of known whole grain oat flours of lower oat bran and β-glucan contents.
There is also a continuing need for the methods of preparing high quality fine oat flour characterized by low levels of bran and beta glucan content for the preparation of oat based RTE cereals of high puffability and low density.
There is also a continuing need for simpler commercially practical methods for β-glucan extraction techniques having high levels of total β-glucan extraction as well as providing high concentrations of β-glucan in the oat flour.
Surprisingly, methods have now been discovered that satisfy these needs. These methods involve dry milling fractionation methods that can be conveniently practiced using known milling equipment and systems in commercial oat milling facilities.